Fabrication and characterization of heparin-grafted poly-L-lactic acid-chitosan core-shell nanofibers scaffold for vascular gasket

Improving hemocompatibility in tissue-engineered products employing heparin-loaded nanoplatforms

The enhancement of hemocompatibility through the use of nanoplatforms loaded with heparin represents a highly desirable characteristic in the context of emerging tissue engineering applications. The significance of employing heparin in biological processes is unquestionable, owing to its ability to interact with a diverse range of proteins. It plays a crucial role in numerous biological processes by engaging in interactions with diverse proteins and hydrogels. This review provides a summary of recent endeavors focused on augmenting the hemocompatibility of tissue engineering methods through the utilization of nanoplatforms loaded with heparin. This study also provides a comprehensive review of the various applications of heparin-loaded nanofibers and nanoparticles, as well as the techniques employed for encapsulating heparin within these nanoplatforms. The biological and physical effects resulting from the encapsulation of heparin in nanoplatforms are examined. The potential applications of heparin-based materials in tissue engineering are also discussed, along with future perspectives in this field.

Thrombogenicity assessment of perfusable tissue engineered constructs: a systematic review

Vascular surgery faces a critical demand for novel vascular grafts that are biocompatible and thromboresistant. This urgency particularly applies to bypass operations involving small caliber vessels. In the realm of tissue engineering, the development of fully vascularized organs holds great promise as a solution to organ shortage for transplantation. To achieve this, it is imperative to (re-)construct a biocompatible and non-thrombogenic vascular network within these organs. In this systematic review, we identify, classify and discuss basic principles and methods used to perform in vitro/ex vivo dynamic thrombogenicity testing of perfusable tissue engineered organs and tissues. We conducted a pre-registered systematic review of studies published in the last 23 years according to PRISMA-P Guidelines, comprising a systematic data extraction, in-depth analysis and risk of bias assessment of 116 included studies. We identified shaking (n=28), flow loop (n=17), ex vivo (arterio-venous shunt, n=33) and dynamic in vitro models (n=38) as main approaches for thrombogenicity assessment. This comprehensive review unveils a prevalent lack of standardization and serves as a valuable guide in the design of standardized experimental setups.

A review of advanced hydrogels for cartilage tissue engineering

With the increase in weight and age of the population, the consumption of tobacco, inappropriate foods, and the reduction of sports activities in recent years, bone and joint diseases such as osteoarthritis (OA) have become more common in the world. From the past until now, various treatment strategies (e.g., microfracture treatment, Autologous Chondrocyte Implantation (ACI), and Mosaicplasty) have been investigated and studied for the prevention and treatment of this disease. However, these methods face problems such as being invasive, not fully repairing the tissue, and damaging the surrounding tissues. Tissue engineering, including cartilage tissue engineering, is one of the minimally invasive, innovative, and effective methods for the treatment and regeneration of damaged cartilage, which has attracted the attention of scientists in the fields of medicine and biomaterials engineering in the past several years. Hydrogels of different types with diverse properties have become desirable candidates for engineering and treating cartilage tissue. They can cover most of the shortcomings of other treatment methods and cause the least secondary damage to the patient. Besides using hydrogels as an ideal strategy, new drug delivery and treatment methods, such as targeted drug delivery and treatment through mechanical signaling, have been studied as interesting strategies. In this study, we review and discuss various types of hydrogels, biomaterials used for hydrogel manufacturing, cartilage-targeting drug delivery, and mechanosignaling as modern strategies for cartilage treatment.

The engineering, drug release, and in vitro evaluations of the PLLA/HPC/Calendula Officinalis electrospun nanofibers optimized by Response Surface Methodology

A system based on poly(l-lactic acid) (PLLA) and hydroxypropyl cellulose (HPC) was considered in this study to achieve electrospun mats with outstanding properties and applicability in biomedical engineering. A novel binary solvent system of chloroform/N,N-dimethylformamide (CF/DMF:70/30) was utilized to minimize the probable phase separation between the polymeric components. Moreover, Response Surface Methodology (RSM) was employed to model/optimize the process. Finally, to scrutinize the ability of the complex in terms of drug delivery, Calendula Officinalis (Marigold) extract was added to the solution of the optimal sample (Opt.PH), and then the set was electrospun (PHM). As a result, the presence of Marigold led to higher values of fiber diameter (262 ± 34 nm), pore size (483 ± 102 nm), and surface porosity (81.0 ± 7.3 %). As this drug could also prohibit the micro-scale phase separation, the PHM touched superior tensile strength and Young modulus of 11.3 ± 1.1 and 91.2 ± 4.2 MPa, respectively. Additionally, the cumulative release data demonstrated non-Fickian diffusion with the Korsmeyer-Peppas exponent and diffusion coefficient of n = 0.69 and D = 2.073 × 10-14 cm2/s, respectively. At the end stage, both the Opt.PH and PHM mats manifested satisfactory results regarding the hydrophilicity and cell viability/proliferation assessments, reflecting their high potential to be used in regenerative medicine applications.

Green and Sustainable Membranes: A review

Membranes are ubiquitous tools for modern water treatment technology that critically eliminate hazardous materials such as organic, inorganic, heavy metals, and biomedical pollutants. Nowadays, nano-membranes are of particular interest for myriad applications such as water treatment, desalination, ion exchange, ion concentration control, and several kinds of biomedical applications. However, this state-of-the-art technology suffers from some drawbacks, e.g., toxicity and fouling of contaminants, which makes the synthesis of green and sustainable membranes indeed safety-threatening. Typically, sustainability, non-toxicity, performance optimization, and commercialization are concerns centered on manufacturing green synthesized membranes. Thus, critical issues related to toxicity, biosafety, and mechanistic aspects of green-synthesized nano-membranes have to be systematically and comprehensively reviewed and discussed. Herein we evaluate various aspects of green nano-membranes in terms of their synthesis, characterization, recycling, and commercialization aspects. Nanomaterials intended for nano-membrane development are classified in view of their chemistry/synthesis, advantages, and limitations. Indeed, attaining prominent adsorption capacity and selectivity in green-synthesized nano-membranes requires multi-objective optimization of a number of materials and manufacturing parameters. In addition, the efficacy and removal performance of green nano-membranes are analyzed theoretically and experimentally to provide researchers and manufacturers with a comprehensive image of green nano-membrane efficiency under real environmental conditions.

Hyaluronic acid/platelet rich plasma-infused core-shell nanofiber membrane to prevent postoperative tendon adhesion and promote tendon healing

An anti-adhesive barrier membrane incorporating hyaluronic acid (HA) can reduce fibroblasts attachment and impart lubrication effect for smooth tendon gliding during management of post-surgical tendon adhesion. On the other hand, as numerous growth factors are required during tendon recovery, growth factors released by platelets in platelet-rich plasma (PRP) can provide beneficial therapeutic effects to facilitate tendon recovery post tendon injury. Furthermore, PRP is reported to be associated with anti-inflammatory properties for suppressing postoperative adhesion. Toward this end, we fabricate core-shell nanofiber membranes (NFM) with HA/PRP-infused core and polycaprolactone shell in this study. Different NFM with 100 % (H-P), 75 % (HP31-P), 50 % (HP11-P) and 25 % (H31-P) HA in the core was fabricated through coaxial electrospinning and analyzed through microscopic, pore size, mechanical, as well as HA and growth factor release studies. In vitro study with fibroblasts indicates the NFM can act as a barrier to prevent cell penetration and reduce cell attachment/focal adhesion, in addition to promoting tenocyte migration in tendon healing. In vivo studies in a rabbit flexor tendon rupture model indicates the HP11-P NFM shows improved efficacy over H-P NFM and control in reducing tendon adhesion formation and inflammation, while promoting tendon healing, from functional assays and histological analysis.

Chitosan-Heparin Polyelectrolyte Multilayer-Modified Poly(vinyl alcohol) Vascular Patches based on a Decellularized Scaffold for Vascular Regeneration

Vascular patches play an important role in vascular reparation and cardiovascular diseases therapy. Recently, decellularized scaffold (DCS)-based vascular patches have drawn attention for their good biocompatibility and blood compatibility. In this work, we developed a poly(vinyl alcohol)-coated DCS as a vascular patch for vascular regeneration. Polyelectrolyte multilayers (PEMs) were further decorated on the surface via layer-by-layer (LbL) self-assembly to improve the biocompatibility of the vascular patch. According to the in vitro experiment, the vascular patch exhibited rapid endothelialization and good hemocompatibility. Compared with unmodified poly(vinyl alcohol)/DCS, the PEM-modified vascular patch possesses improved hemocompatibility, for example, enhanced anti-platelet adhesion ability, prolonged in vitro coagulation time, and decreased hemolysis rate. Therefore, this vascular patch is conducive to the proliferation and attachment of endothelial progenitor cells. Meanwhile, the in vivo performance in a porcine model was investigated with the in vivo computed tomography angiography and B ultrasound was used to further confirm the vascular regeneration. Excitedly, the porcine artery could remain unblocked for 5 months after implantation. Our current research provides a potential strategy for treating diseased blood vessels in clinical surgery.

Evidence for bicomponent fibers: A review

Recently, bicomponent fibers have been attracting much attention due to their unique structural characteristics and properties. A common concern was how to characterize a bicomponent fiber. In this review, we generally summarized the classification, structural characteristics, preparation methods of the bicomponent fibers, and focused on the experimental evidence for the identification of bicomponent fibers. Finally, the main challenges and future perspectives of bicomponent fibers and their characterization are provided. We hope that this review will provide readers with a comprehensive understanding of the design and characterization of bicomponent fibers.

Reviewing Chitin/Chitosan Nanofibers and Associated Nanocomposites and Their Attained Medical Milestones

Chitin/chitosan research is an expanding field with wide scope within polymer research. This topic is highly inviting as chitin/chitosan's are natural biopolymers that can be recovered from food waste and hold high potentials for medical applications. This review gives a brief overview of the chitin/chitosan based nanomaterials, their preparation methods and their biomedical applications. Chitin nanofibers and Chitosan nanofibers have been reviewed, their fabrication methods presented and their biomedical applications summarized. The chitin/chitosan based nanocomposites have also been discussed. Chitin and chitosan nanofibers and their binary and ternary composites are represented by scattered superficial reports. Delving deep into synergistic approaches, bringing up novel chitin/chitosan nanocomposites, could help diligently deliver medical expectations. This review highlights such lacunae and further lapses in chitin related inputs towards medical applications. The grey areas and future outlook for aligning chitin/chitosan nanofiber research are outlined as research directions for the future.

Blood biocompatibility enhancement of biomaterials by heparin immobilization: a review

Blood contacting materials are concerned with biocompatibility including thrombus formation, decrease blood coagulation time, hematology, activation of complement system, platelet aggression. Interestingly, recent research suggests that biocompatibility is increasing by incorporating various materials including heparin using different methods. Basic of heparin including uses and complications was mentioned, in which burst release of heparin is major issue. To minimize the problem of biocompatibility and unpredictable heparin release, present review article potentially reviews the reported work and investigates the various immobilization methods of heparin onto biomaterials, such as polymers, metals, and alloys. Detailed explanation of different immobilization methods through different intermediates, activation, incubation method, plasma treatment, irradiations and other methods are also discussed, in which immobilization through intermediates is the most exploitable method. In addition to biocompatibility, other required properties of biomaterials like mechanical and corrosion resistance properties that increase by attachment of heparin are reviewed and discussed in this article.

Fabrication of Biomedical Scaffolds Using Biodegradable Polymers

Degradable polymers are used widely in tissue engineering and regenerative medicine. Maturing capabilities in additive manufacturing coupled with advances in orthogonal chemical functionalization methodologies have enabled a rapid evolution of defect-specific form factors and strategies for designing and creating bioactive scaffolds. However, these defect-specific scaffolds, especially when utilizing degradable polymers as the base material, present processing challenges that are distinct and unique from other classes of materials. The goal of this review is to provide a guide for the fabrication of biodegradable polymer-based scaffolds that includes the complete pathway starting from selecting materials, choosing the correct fabrication method, and considering the requirements for tissue specific applications of the scaffold.

Chitosan coated pH-responsive metal-polyphenol delivery platform for melanoma chemotherapy

The safe and effective drug delivery system is important for cancer therapy. Here in, we first constructed a delivery system Cabazitaxel(Cab)@MPN/CS between metal-polyphenol (MPN) and chitosan (CS) to deliver Cab for melanoma therapy. The preparation process is simple, green, and controllable. After introducing CS coating, the drug loading was improved from 7.56 % to 9.28 %. Cab@MPN/CS NPs released Cab continuously under acid tumor microenvironment. The zeta potential of Cab@MPN/CS NPs could be controlled by changing the ratio of Cab@MPN and CS solutions. The positively charged Cab@MPN/CS accelerate B16F10 cell internalization. After internalized, Cab@MPN/CS NPs could escape from lysosomes via the proton sponge effect. The permeability of CS promotes the penetration of Cab@MPN/CS to the deeper B16F10 tumor spheroids. In vivo results showed that Cab@MPN/CS NPs have a longer retention time in tumor tissues and significantly inhibit tumor growth by up-regulating TUNEL expression and down-regulating KI67 and CD31 expression. Thus, this delivery system provides a promising strategy for the tumor therapy in clinic.

Interactions at engineered graft-tissue interfaces: A review

The interactions at the graft-tissue interfaces are critical for the results of engraftments post-implantation. To improve the success rate of the implantations, as well as the quality of the patients' life, understanding the possible reactions between artificial materials and the host tissues is helpful in designing new generations of material-based grafts aiming at inducing specific responses from surrounding tissues for their own reparation and regeneration. To help researchers understand the complicated interactions that occur after implantations and to promote the development of better-designed grafts with improved biocompatibility and patient responses, in this review, the topics will be discussed from the basic reactions that occur chronologically at the graft-tissue interfaces after implantations to the existing and potential applications of the mechanisms of such reactions in designing of grafts. It offers a chance to bring up-to-date advances in the field and new strategies of controlling the graft-tissue interfaces.

Stereocomplexed electrospun nanofibers containing poly (lactic acid) modified quaternized chitosan for wound healing

Skin damage, especially the extensive full-thickness wound, is seriously affecting people's daily life and health. Meanwhile, wound healing is always challenged by bacterial infection. In this study, for the purpose of developing a disinfectant wound dressing, we designed a novel multi-functional nanofiber mats via electrospinning combining chitosan derivations and stereocomplex crystallite (SC). The SC membrane of poly (lactic acid)/chitosan derivatives were prepared via warming at 80 °C for 1 h. The thermal and mechanical properties of the heated mats were strengthened owing to the formation of SC, which restricted the lactide chains mobility. In vivo wound healing test revealed that the SC mats have better wound repair ability than the control group with a wound healing rate of 100 % within 15 days. In a word, the biomass-based mats with enhanced thermal and mechanical properties, antibacterial effect and antioxidant activity, providing a potential multi-functional platform for designing of disinfectant wound dressings.

Biodegradable Nanopolymers in Cardiac Tissue Engineering: From Concept Towards Nanomedicine

Cardiovascular diseases are the number one cause of heart failure and death in the world, and the transplantation of the heart is an effective and viable choice for treatment despite presenting many disadvantages (most notably, transplant heart availability). To overcome this problem, cardiac tissue engineering is considered a promising approach by using implantable artificial blood vessels, injectable gels, and cardiac patches (to name a few) made from biodegradable polymers. Biodegradable polymers are classified into two main categories: natural and synthetic polymers. Natural biodegradable polymers have some distinct advantages such as biodegradability, abundant availability, and renewability but have some significant drawbacks such as rapid degradation, insufficient electrical conductivity, immunological reaction, and poor mechanical properties for cardiac tissue engineering. Synthetic biodegradable polymers have some advantages such as strong mechanical properties, controlled structure, great processing flexibility, and usually no immunological concerns; however, they have some drawbacks such as a lack of cell attachment and possible low biocompatibility. Some applications have combined the best of both and exciting new natural/synthetic composites have been utilized. Recently, the use of nanostructured polymers and polymer nanocomposites has revolutionized the field of cardiac tissue engineering due to their enhanced mechanical, electrical, and surface properties promoting tissue growth. In this review, recent research on the use of biodegradable natural/synthetic nanocomposite polymers in cardiac tissue engineering is presented with forward looking thoughts provided for what is needed for the field to mature.

Localized delivery of active targeting micelles from nanofibers patch for effective breast cancer therapy

Nanofibers based transdermal drug delivery is a promising platform, and it effectively delivers the drug to tumor sites. The objective of the study was to fabricate stimuli-responsive polymeric nanofibers encapsulated with an active targeting micellar system for in situ drug delivery. Stimuli-responsive core-shell nanofibers release thedrug at target sites with minimum side effects to the other organs, decrease the drug administration concentration. Initially, we prepared CA conjugated PCPP polymeric micelles loaded with PTX. Then, core-shell nanofibers were prepared using PHM with coaxial electrospinning and distinct core-shell nanofibers formation confirm by SEM and TEM. Nanofibers showed a homogenous distribution of micelles inside the fiber mesh, diffusion, and erosion processes lead to a controlled release of PTX.In vitro drug release and swelling, revealed the pH based sustained release of the drug for 180 h from the nanofibers mat. Functional and stimuli-responsive nanofibers highly absorb H⁺ ions and repulsion of cations promoting maximum swelling to release more drugs in acidic pH. An increased transportation rate of 70% drug release through epidermis for 120 h. Nanofibers effectively internalize to the skin, and it confirmed by confocal microscopy. MCF-7 cells grown and spread over the nanofibers, which show the biocompatibility of nanofibers. Compared to PTX, drug-loaded nanofibers exhibited higher cytotoxicity for 8 days which was confirmed by the flow cytometry. These promising results confirm, the novel stimuli-responsive core-shell nanofibers actively target breast cancer cells and lead the way to safe cancer therapy.

Co-culture of mesenchymal stem cells and human umbilical vein endothelial cells on heparinized polycaprolactone/gelatin co-spun nanofibers for improved endothelium remodeling

Endothelization of a tissue-engineered substrate is important for its application as an artificial vascular graft. Despite recent advancements in artificial graft fabrication, a graft of <5 mm is difficult to fabricate owing to insufficient endothelization that results in thrombosis after transplantation. We aimed to perform a co-culture of adipose-derived mesenchymal stem cells (MSCs) with human umbilical vein endothelial cells (HUVECs) on antithrombogenic polycaprolactone (PCL)/heparin-gelatin co-spun nanofibers to evaluate the role of co-culturing in promoting quick endothelization of vascular substrates without surface modification by growth factors or other ECM proteins that trigger the endothelization process. Using a co-axial electrospinning technique, we attempted to fabricate our scaffold balancing between mechanical properties and biocompatibility. Antithrombogenic characteristics were then imparted to the fabricated nanofiber substrate by grafting of heparin. Finally, we performed a co-culture of MSCs and HUVECs on the fabricated co-spun nanofiber substrate to obtain proper endothelization of our material under the in-vitro culture. Staining for CD-31 at seven days of culture revealed enhanced CD-31 expression under the co-culture condition; actin staining revealed healthy cobblestone HUVEC morphology, suggesting that MSCs can aid in proper endothelization. Hence, we conclude that co-culture is effective for quick endothelization of vascular substrates.

Electrospun acid-neutralizing fibers for the amelioration of inflammatory response

Biodegradable aliphatic polyesters, especially polylactide (PLA), polyglycolide (PGA), and their copolymer poly(lactide-co-glycolide) (PLGA), are the most representative and widely used synthetic polymers in the field of tissue engineering and regenerative medicine. However, these polyesters often give rise to aseptic inflammation because of their acidic degradation products after implantation. Here, unidirectional shell-core structured fibers of chitosan/poly(lactide-co-glycolide) (i.e., CTS/PLGA) with acid-neutralizing capability were developed for addressing the noted issue by coating the PLGA fiber surfaces with a layer of the alkaline chitosan by coaxial electrospinning. Our results showed that during a period of 8-week degradation, the shell-layer of chitosan with its unique alkaline nature for acid-neutralization obviously hindered the pH decrease as a result of the degradation of PLGA-core. In a mocked acidic environment testing of the human dermal fibroblasts, chitosan-enabled acidity neutralization could significantly reduce in vitro the secretion of inflammatory factors and downregulate the expression of related inflammatory genes. Thereafter, biocompatibility assessment in vitro showed that the CTS/PLGA fibers had poorer cell adhesion capacity than the PLGA fibers but were cytocompatible and promoted cell migration and secretion of collagen. Moreover, subcutaneous embedding for two and four weeks in vivo revealed that the CTS/PLGA fibers significantly reduced the recruitment of inflammatory cells and the formation of foreign body giant cells (FBGCs). This study thereby demonstrated the evident acid-neutralizing effect of the chitosan-coating layer on alleviating the inflammatory responses caused by the acidic degradation products of the PLGA-core. Our highly aligned CTS/PLGA fibers, as a kind of quasi "pH-neutral fibers" with the acid-neutralizing capability, could be potentially applied for engineering those architecturally anisotropic tissues (e.g., tendon/ligament) toward improved efficacy of regeneration. STATEMENT OF SIGNIFICANCE: It is well known that acidic degradation products from representative aliphatic polyesters (e.g., PLA, PGA, and PLGA) give rise to the problem of aseptic inflammation. Various alkaline components acting as neutralizing agents have been used to address the noted issue. However, rather less attention has been paid to engineer these polyesters into a fibrous form with acid-neutralizing functionality. The present study proposes the concept of "pH-neutral fibers" and develops shell-core structured unidirectional fibers of chitosan/poly(lactide-co-glycolide) with acid-neutralizing capability for ameliorating inflammatory responses caused by the acidic degradation products of PLGA. It provides a comprehensive study encompassing fiber characterization and in vitro and in vivo evaluation, which would pave the way for developing sophisticated pH-neutral fibers for functional tissue regeneration.

Coaxial Electrospinning Formation of Complex Polymer Fibers and their Applications

The formation of fibers by electrospinning has experienced explosive growth in the past decade, recently reaching 4,000 publications and 1,500 patents per year. This impressive growth of interest is due to the ability to form fibers with a variety of materials, which lend themselves to a large and rapidly expanding set of applications. In particular, coaxial electrospinning, which forms fibers with multiple core-sheath layers from different materials in a single step, enables the combination of properties in a single fiber that are not found in nature in a single material. This article is a detailed review of coaxial electrospinning: basic mechanisms, early history and current status, and an in-depth discussion of various applications (biomedical, environmental, sensors, energy, catalysis, textiles). We aim to provide readers who are currently involved in certain aspects of coaxial electrospinning research an appreciation of other applications and of current results.

Cytotoxicity, bactericidal and hemostatic evaluation of oxidized cellulose microparticles: Structure and oxidation degree approach

Oxidized cellulose is the most used hemostatic materials in clinical applications. In addition to its perfect hemostatic efficiency, it is degradable under in vivo conditions and supremely prevents bacterial growth. On the other hand, one of the drawbacks of the oxidized cellulose is cytotoxicity due to the strongly acidic nature during degradation. There is a number of commercially available oxidized cellulose products which are derived from regenerated and non-regenerated cellulose. On the other hand, the effect of oxidation degree and structure (regenerated or non-regenerated) on product efficiency is undetermined. Moreover, oxidation degree which is primary factor for both bactericidal and hemostatic efficiency is also crucial for assessment of the product. In this study, oxidized cellulose versus oxidized regenerated cellulose microparticles with various oxidation degree was produced and characterized. Comparative studies were conducted in terms of bactericidal and hemostatic efficiencies in addition to cytotoxicity. The results could be a reference for the optimized oxidized cellulose product for the hemostatic applications.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

[Preparation and osteogenic properties of poly ( L-lactic acid)/lecithin porous scaffolds with open pore structure]

Objective

To investigate the preparation and osteogenic properties of poly ( L-lactic acid)(PLLA)/lecithin porous scaffolds with open pore structure.

Methods

PLLA/lecithin porous scaffolds with different lecithin contents (0, 5%, 10%, 20%, 30%, 40%, 50%) were prepared by thermally induced phase separation (groups A, B, C, D, E, F, and G, respectively). Scanning electron microscopy (SEM) was used to observe the surface morphology of the scaffolds. Wide-angle X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to detect the crystallinity of the scaffolds. The water uptake ability of the scaffolds was measured. The cell growth and viability of bone marrow mesenchymal stem cells (BMSCs) of mouse on each scaffold was assessed by cell counting kit 8 (CCK-8) method. The osteogenic differentiation ability of BMSCs on each scaffold was evaluated by alkaline phosphatase (ALP) activity. Finally, a critical-size rat calvarial bone defect model was used to evaluate the osteogenesis of the scaffolds in vivo. Micro-CT was used to reconstruct the three-dimensional model of the defect area, and the bone volume and bone mineral density were quantitatively analyzed.

Results

SEM results showed that the lecithin could slightly reduce the pore size; when lecithin content was 50%, platelet-like structure could be observed on the scaffolds. Wide angle XRD and DSC showed that the crystallinity of scaffolds gradually decreased with the increase of lecithin content. The water uptake ability test showed that the hydrophilicity of scaffolds increased with the increase of lecithin content. CCK-8 assay showed that cell activity gradually increased with the increase of culture time. After 7 days of culture, the absorbance ( A) value of groups C, D, E, and F were significantly higher than that of groups A, B, and G ( P<0.05), but no significant difference was found among groups C, D, E, and F ( P>0.05). After 14 days of osteogenic induction, with the increase of lecithin content, there was a significant difference in ALP activity of each group. The ALP activity in groups D, E, F, and G were significantly higher than that in groups A, B, and C ( P<0.05). In vivo, the results of Micro-CT examination and bone volume and bone mineral density showed that the scaffolds with 30% lecithin had the best repairing effect.

Conclusion

Prepared by thermally induced phase separation, the cytocompatibility, osteogenic differentiation, and bone repair ability of the PLLA/lecithin porous scaffold is obviously better than that of pure PLLA scaffold. PLLA/lecithin porous scaffold with suitable lecithin content is a promising scaffold material for bone tissue engineering.

Biomimetic composite scaffold of hydroxyapatite/gelatin-chitosan core-shell nanofibers for bone tissue engineering

Good biocompatibility and osteogenesis of three-dimensional porous scaffolds are critical for bone tissue engineering. In this work, biomimetic hydroxyapatite/gelatin-chitosan core-shell nanofibers composite scaffolds have been fabricated to mimic both the specific structure and the chemical composition of natural bone. The coaxial electrospinning technique was introduced to prepare gelatin-chitosan core-shell structured nanofibers mat which formed three-dimensional porous structure for promoting cells growth. The gelatin-chitosan core-shell nanofibers formed Arginine-Glycine-Aspartic acid (RGD)-like structure to mimic the organic component of natural bone extracellular matrix. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP), as the major mineral constituent of native bone, was then deposited onto the surface of gelatin-chitosan core-shell structured nanofibers by a wet chemical method. Compared with chitosan nanofibers, gelatin nanofibers and chitosan-gelatin composite nanofibers, gelatin-chitosan core-shell structured nanofibers improved the mineralization efficiency of hydroxyapatite and formed a homogeneous HAP deposit. When Human osteoblast like cell line (MG-63) were cultured on the materials, the results showed that hydroxyapatite deposited on the gelatin-chitosan core-shell structured nanofibers could further enhance osteoblast cell proliferation. The biomimetic composite scaffolds could be suggested as a promising material to promote osteoblast cell growth in bone tissue engineering.

Functionalized core/shell nanofibers for the differentiation of mesenchymal stem cells for vascular tissue engineering

AIM

Atherosclerosis is a common cardiovascular disease causing medical problems globally leading to coronary artery bypass surgery. The present study is to fabricate core/shell nanofibers to encapsulate VEGF for the differentiation of mesenchymal stem cells (MSCs) into smooth muscle cells to develop vascular grafts.

MATERIALS & METHODS

The fabricated core/shell nanofibers contained polycaprolactone/gelatin as the shell, and silk fibroin/VEGF as the core materials.

RESULTS

The results observed that the core/shell nanofibers interact to differentiate MSCs into smooth muscle cells by the expression of vascular smooth muscle cell (VSMC) contractile proteins α-actinin, myosin and F-actin.

CONCLUSION

The functionalized polycaprolactone/gelatin/silk fibroin/VEGF (250 ng) core/shell nanofibers were fabricated for the controlled release of VEGF in a persistent manner for the differentiation of MSCs into smooth muscle cells for vascular tissue engineering.

Strengthened and Thermally Resistant Poly(lactic acid)-Based Composite Nanofibers Prepared via Easy Stereocomplexation with Antibacterial Effects

Strengthened poly(lactic acid) (PLA)-based materials with improved mechanical performance and improved thermal resistance, notably, are prepared by introducing stereocomplex crystallite (SC), an ideal filler, into the materials. Owing to the intermolecular hydrogen bond among the stereoisomer chains, the melting point of the special crystallite is up to 200 °C, which is 50 °C higher than the isostatic crystallite. The modulus of the PLA-based materials can be enhanced to several 100 MPa because of the integrated polymer chain arrangement. In this study, we electrospun hybrid nanofibers consisted of PLA stereoisomers and induced the stereocomplex crystallization under a mild condition (65 °C for 1 h). The mild warming is favorable for the protection of chlorogenic acid (CA) that was selected as the antibacterial agent. Both of Gram-positive and Gram-negative bacteria were efficiently cleared away using the warmed nanofibers that released CA rapidly within just a few hours. Used as filters, the SC electrospinning membrane also presented a potent filtering effect, leaving no bacteria retained in the filtrates. Attributing to SC, the PLA-based nanofibers showed extremely increased melting temperature over 200 °C and improved Young's modulus up to 270.0 MPa. The durable nanofibers prepared in present study are meaningful for enlarging the application of PLA-based materials, for example, as filters, masks, and packages.

Synergistic Effects of Electrical Stimulation and Aligned Nanofibrous Microenvironment on Growth Behavior of Mesenchymal Stem Cells

Incontrollable cellular growth behavior is a significant issue, which severely affects the functional tissue formation and cellular protein expression. Development of natural extracellular matrix (ECM) like biomaterials to present microenvironment cues for regulation of cell responses can effectively overcome this problem. The external simulation and topological characteristics as typical guiding cues are capable of providing diverse influences on cellular growth. Herein, we fabricated two-dimensional aligned conductive nanofibers (2D-ACNFs) by an electrospinning process and surface polymerization, and the obtained 2D-ACNFs provided the effects of both alignment and electrical stimulation (ES) on cellular response of human mesenchymal cells (hMSCs). The results of cellular responses implied that the obtained 2D-ACNFs could offer a synergistic effect of both ES and aligned nanopattern on hMSC growth behavior. The effects could not only promote hMSCs to contact each other and maintain cellular activity but also provide positive promotion to regulate cellular proliferation. Thus, we believe that the obtained 2D-ACNFs will have a broad application in the biomedical field, such as cell culture with ES, directional induction for cell growth, and damaged tissue repair, etc.

An aptasensor based on heparin-mimicking hyperbranched polyester with anti-biofouling interface for sensitive thrombin detection

In this paper, novel heparin-mimicking hyperbranched polyester nanoparticles (HBPE-SO₃ NPs) with abundant of sulfonated acid functional groups were synthesized, and their antithrombogenicities were further evaluated. Further, a label-free electrochemical aptamer biosensor (aptasensor) based on HBPE-SO₃ NPs modified electrode was developed for thrombin (TB) detection in whole blood. Meanwhile, the anti-biofouling properties of different modified electrodes were studied by whole blood and platelet adhesion test, hemolysis assay and morphological changes of red blood cells in vitro. Besides, the thrombin-binding aptamer was selected as receptor for the proposed aptasensor, which has excellent binding affinity and selectivity for TB. When binding to TB, the electron transfer taking place at the modified electrode interface was inhibited that can attribute to the stereo-hindrance effect, resulting in the decreased current response. This aptasensor showed excellent electrochemical properties with a wide detection range and a low detection limit of 0.031pM (S/N = 3), and provided high selectivity, long-term stability and good reproducibility. Finally, the sensitively detection of TB in whole blood samples directly was achieved by this aptasensor we proposed, which suggested its great potential for TB detection in the clinic.

Polylactic Acid Nanofiber Scaffold Decorated with Chitosan Islandlike Topography for Bone Tissue Engineering

In this work, a bicomponent scaffold with a core-shell and islandlike structure that combines the respective advantages of polylactic acid (PLA) and chitosan (CS) was prepared via electrospinning accompanied by automatic phase separation and crystallization. The objective of this research was to design nanosized topography with highly bioactive CS onto PLA electrospun fiber surface to improve the cell biocompatibility of the PLA fibrous membrane. The morphology, inner structure, surface composition, crystallinity, and thermodynamic analyses of nanofibers with various PLA/CS ratios were carried out, and the turning mechanism of a core-shell or islandlike topography structure was also speculated. The mineralization of hydroxyapatite and culture results of preosteoblast (MC3T3-E1) cells on the modified scaffolds indicate that the outer CS component and rough nanoscale topography on the surface of the nanofibers balanced the hydrophilicity and hydrophobicity of the fibers, enhanced their mineralization ability, and made them more beneficial for the attachment and growth of cells. Moreover, CS and "islandlike" protrusions on the fiber surface increased the alkaline phosphatase activity of the MC3T3-E1 cells seeded on the fibrous membrane and provided a more appropriate interface for cell adhesion and proliferation. These results illustrate that this kind of PLA/CS membrane has the potential in tissue engineering. More importantly, our study provides a new approach to designing PLA scaffolds, with combined topographic and bioactive modification effects at the interface between cells and materials, for biomedicine.

Repairing a bone defect with a three-dimensional cellular construct composed of a multi-layered cell sheet on electrospun mesh

In addition to providing maneuverability, electrospun nanofibrous meshes can make excellent supports for constructing flexible cell sheets to regulate cell behavior by nanofiber features. With the target of bone regeneration, herein composite nanofibers with two different fiber arrangements (nestlike, random) were electrospun from a blend solution containing poly(l-lactide) (PLLA) and gelatin (1:1 in weight ratio). Unlike the non-woven morphology in a random nanofibrous mesh, PLLA/gelatin composite nanofibers in the nestlike nanofibrous mesh displayed both non-woven and parallel morphologies. Both kinds of nanofibrous mesh were ∼50 μm thick as-prepared, and shrank to ∼30 μm after seeding with bone mesenchymal stromal cells (BMSCs). After 7 days of in vitro culture, cell sheets could form on both meshes (CSM) and on the culture plate. It was found that application of nanofibrous mesh promoted the osteogenic differentiation of BMSC sheets compared with the control. The nestlike mesh displayed slight superiority over the random mesh in enhancing osteogenic differentiation, but their different fiber arrangements did not cause much difference in cell proliferation. Three-dimensional multi-layered CSM constructs were built by stacking four mono-layered CSMs together. The CSM constructs (based on a nestlike or random nanofibrous mesh) were incubated in vitro for 3 days before being implanted into rat cranial defects. In comparison with the control group, there was significant formation of new calcified bone in both CSM construct-filled groups at 12 weeks' post-operation. The nestlike group showed slightly better bone healing (based on both qualitative and quantitative analysis) than the random group, while showing insignificant differences. We showed that the concept of using a three-dimensional multi-layered CSM construct in enhancing bone regeneration was feasible. Future studies should take more nanofiber features (e.g. bioactive components) into account to further enhance osteogenesis.

Injectable hydrogels for cartilage and bone tissue engineering

Tissue engineering has become a promising strategy for repairing damaged cartilage and bone tissue. Among the scaffolds for tissue-engineering applications, injectable hydrogels have demonstrated great potential for use as three-dimensional cell culture scaffolds in cartilage and bone tissue engineering, owing to their high water content, similarity to the natural extracellular matrix (ECM), porous framework for cell transplantation and proliferation, minimal invasive properties, and ability to match irregular defects. In this review, we describe the selection of appropriate biomaterials and fabrication methods to prepare novel injectable hydrogels for cartilage and bone tissue engineering. In addition, the biology of cartilage and the bony ECM is also summarized. Finally, future perspectives for injectable hydrogels in cartilage and bone tissue engineering are discussed.

Fabrication of chitosan/PEO nanofiber mats with mica by electrospinning

Chitosan (CS) is an excellent biocompatible natural antibacterial material that has attracted researchers to study its biological applications as artificial tissue scaffolds and wound-healing materials. In this research, CS has been mixed with polyethylene oxide (PEO) and mica at various weight ratios to prepare nanofibers; however, it is found to be a difficult task to prepare the nanofiber using pure CS. The composite in form of nanofibrous mat was prepared with CS/PEO solution and CS/PEO/mica solution using electrospinning. Processing conditions were adjusted to a flow rate of 6 ml/min, with an applied voltage of 27 kV. The distance of capillary tip to target was kept about 10 cm at 25°C with a collector having a speed of 200 rpm. The spinnability of solutions was also evaluated by using both plate and cylinder collectors. The composite mats were analyzed in detail using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis, and X-ray diffractogram (XRD). SEM photomicrograms indicated that the morphology and diameter of the nanofibers were affected by weight ratio of CS/PEO, concentration of mica, and types of collector. Furthermore, mica was incorporated in the CS/PEO matrix to enhance the specific surface area. Molecular interactions between CS/PEO and mica were investigated using FTIR and XRD.

Fabrication and hemocompatibility assessment of novel polyurethane-based bio-nanofibrous dressing loaded with honey and Carica papaya extract for the management of burn injuries

Management of burn injury is an onerous clinical task since it requires continuous monitoring and extensive usage of specialized facilities. Despite rapid improvizations and investments in burn management, >30% of victims hospitalized each year face severe morbidity and mortality. Excessive loss of body fluids, accumulation of exudate, and the development of septic shock are reported to be the main reasons for morbidity in burn victims. To assist burn wound management, a novel polyurethane (PU)-based bio-nanofibrous dressing loaded with honey (HN) and Carica papaya (PA) fruit extract was fabricated using a one-step electrospinning technique. The developed dressing material had a mean fiber diameter of 190±19.93 nm with pore sizes of 4–50 µm to support effective infiltration of nutrients and gas exchange. The successful blending of HN- and PA-based active biomolecules in PU was inferred through changes in surface chemistry. The blend subsequently increased the wettability (14%) and surface energy (24%) of the novel dressing. Ultimately, the presence of hydrophilic biomolecules and high porosity enhanced the water absorption ability of the PU-HN-PA nanofiber samples to 761.67% from 285.13% in PU. Furthermore, the ability of the bio-nanofibrous dressing to support specific protein adsorption (45%), delay thrombus formation, and reduce hemolysis demonstrated its nontoxic and compatible nature with the host tissues. In summary, the excellent physicochemical and hemocompatible properties of the developed PU-HN-PA dressing exhibit its potential in reducing the clinical complications associated with the treatment of burn injuries.

Advantages and challenges offered by biofunctional core-shell fiber systems for tissue engineering and drug delivery

Whereas highly porous scaffolds composed of electrospun nanofibers can mimick major features of the extracellular matrix in tissue engineering, they lack the ability to incorporate and release biocompounds (drugs, growth factors) safely in a controlled way. Here, electrospun core-shell fibers (core made from water and aqueous solutions of hydrophilic polymers and the shell from materials with well-defined release mechanisms) offer unique advantages in comparison with those that have helped make porous nanofibrillar scaffolds highly successful in tissue engineering. This review considers the preparation and biofunctionalization of such core-shell fibers as well as applications in various areas, including neural, vascular, cardiac, cartilage and bone tissue engineering, and touches on the topic of clinical trials.

Hypoxia enhances angiogenesis in an adipose-derived stromal cell/endothelial cell co-culture 3D gel model

OBJECTIVES

This study aimed to investigate the influence of hypoxia on angiogenesis in a 3D gel, with co-culturing adipose-derived stromal cells (ASCs) and endothelial cells (ECs).

MATERIALS AND METHODS

ASCs from green fluorescent protein-labeled mice and ECs from red fluorescent protein-labeled mice were co-cultured in 3D collagen gels at 1:1 ratio, in normal and hypoxic oxygen conditions, and morphology of angiogenesis was observed using confocal laser scanning microscopy. To discover changes in growth factors between monoculture ASCs and ECs, transwell co-cultures of ASCs and ECs were applied. Semi-quantitative PCR was performed to explore mRNA expression of growth factors.

RESULTS

Enhanced angiogenesis was observed in 3D gels implanted with 1:1 mixture of ASCs and ECs after 7 days hypoxia. Genes including VEGFA/B, EGF-1, HIF-1a, IGF-1, PDGF, TGF-β1 and BMP-2/4 in ECs, both monoculture and co-culture, were significantly enhanced after being cultured under hypoxia. In comparison, genes VEGFA/B, EGF-1, HIF-1a, TGF-β1 and BMP-2 in ASCs increased. In all, factors VEGFA/B, EGF-1, HIF-1a, TGF-β1 and BMP-2 increased in both ASCs and ECs after being cultured in hypoxia no matter whether as monoculture or co-culture.

CONCLUSIONS

Co-culture of ASCs and ECs at 1:1 ratio in a 3D gel under hypoxia promoted angiogenesis. Those growth factors which were increased in both ASCs and ECs, indicate that VEGFA/B, EGF-1, HIF-1a, TGF-β1 and BMP-2 might be responsible for enhancement in angiogenesis triggered by hypoxia.

Fabrication, Characterization, and Biocompatibility of Polymer Cored Reduced Graphene Oxide Nanofibers

Graphene nanofibers have shown a promising potential across a wide spectrum of areas, including biology, energy, and the environment. However, fabrication of graphene nanofibers remains a challenging issue due to the broad size distribution and extremely poor solubility of graphene. Herein, we report a facile yet efficient approach for fabricating a novel class of polymer core-reduced graphene oxide shell nanofiber mat (RGO-CSNFM) by direct heat-driven self-assembly of graphene oxide sheets onto the surface of electrospun polymeric nanofibers without any requirement of surface treatment. Thus-prepared RGO-CSNFM demonstrated excellent mechanical, electrical, and biocompatible properties. RGO-CSNFM also promoted a higher cell anchorage and proliferation of human bone marrow mesenchymal stem cells (hMSCs) compared to the free-standing RGO film without the nanoscale fibrous structure. Further, cell viability of hMSCs was comparable to that on the tissue culture plates (TCPs) with a distinctive healthy morphology, indicating that the nanoscale fibrous architecture plays a critically constructive role in supporting cellular activities. In addition, the RGO-CSNFM exhibited excellent electrical conductivity, making them an ideal candidate for conductive cell culture, biosensing, and tissue engineering applications. These findings could provide a new benchmark for preparing well-defined graphene-based nanomaterial configurations and interfaces for biomedical applications.